Russia's aviation authority has suspended all flights aboard Boeing 737s until the airplanes' pilots receive additional training after a recent deadly crash in the Ural Mountains city of Perm.

All 88 people aboard the Aeroflot-Nord flight were killed when the Boeing 737-500 crashed while preparing to land on Sept. 14.

Federal Agency of Air Transport spokesman Sergei Samoshin says the agency has suspended flights by planes similar to the one that crashed until their pilots can undergo more training on simulators.

He did not say Thursday how many aircraft would be affected or how long the suspension would last.

Aviation experts and observers say the crash was likely caused by a pilot error.